linux-kernel - RE: [PATCH v4 2/7] iommu: Lock group->mutex in iommu_deferred

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Message-ID: <BL1PR11MB5271F7BD6FF2E99D6C8EC5688C08A@BL1PR11MB5271.namprd11.prod.outlook.com>
Date: Fri, 12 Sep 2025 09:34:11 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "joro@...tes.org" <joro@...tes.org>,
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Subject: RE: [PATCH v4 2/7] iommu: Lock group->mutex in
 iommu_deferred_attach()

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Monday, September 1, 2025 7:32 AM
> 
> The iommu_deferred_attach() function invokes __iommu_attach_device()
> while
> not holding the group->mutex, like other __iommu_attach_device() callers.
> 
> Though there is no pratical bug being triggered so far, it would be better
> to apply the same locking to this __iommu_attach_device(), since the
> IOMMU
> drivers nowaday are more aware of the group->mutex -- some of them use
> the
> iommu_group_mutex_assert() function that could be potentially in the path
> of an attach_dev callback function invoked by the __iommu_attach_device().
> 
> The iommu_deferred_attach() will soon need to verify a new flag stored in
> the struct group_device. To iterate the gdev list, the group->mutex should
> be held for this matter too.
> 
> So, grab the mutex to guard __iommu_attach_device() like other callers.
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>